Association between ridge morphology and complexity of implant placement planning in the posterior mandible.

Statement Of Problem: Uncertainties regarding the 3D ridge morphology of the posterior mandible can greatly increase the risk of surgical complications during dental implant placement. By using cone beam computed tomography (CBCT) imaging and a computer-guided implant treatment software program before any invasive procedure, it is possible to assess ridge morphology and understand the surgical complexity and risk level.

Purpose: The purpose of this radiological clinical study was to evaluate a large series of CBCT images to evaluate ridge shape variations along posterior mandibular edentulous regions and to clarify their associations with the level of implant planning complexity.

Material And Methods: One hundred and twenty CBCT files were analyzed retrospectively for a total 240 hemimandibular sites. Images of each edentulous region of the mandibular first and second premolar and first and second molar sites were evaluated in the sagittal plane. Ridge morphology and implant planning complexity per site were assessed. Categorical variables were presented as number of events and percentages. The chi-square test was used to compare the categorical variables (P=.05).

Results: Of 491 partially edentulous mandibular sites, 235 were on the right, and 256 were on the left. Forty-two sites had a distal adjacent tooth, while 266 sites had no distal adjacent tooth. The sagittal bone sections demonstrated oblique (40.53%), straight (31.77%), S-shape (24.24%), hourglass (2.44%), and basal bone (1.02%) ridge morphologies. Implant complexity was deemed straightforward in 66.19% of sites, while 31.6% were identified as advanced and 2.54% as complex. When ridge morphology was evaluated from straight to basal-round bone shape, the implant complexity followed the same trend of change from a straightforward to complex procedure (P=.001) for edentulous second and first molar regions. No significant differences were noted at edentulous second premolar sites (P=.063). The missing second molar sites with oblique morphology were predicted to have 60.9% straightforward complexity, and first molar sites with oblique morphology had 55.8% straightforward implant complexity. Second premolars with straight ridge morphology had 71.7% straightforward complexity, whereas first premolars with the same shape had 92.5% straightforward implant complexity.

Conclusions: Careful evaluation of sagittal CBCT images can provide significant clinical information regarding ridge shape and anticipated surgical complexity before and at the time of implant placement. Surgical complexity is greatest at the most posterior mandibular edentulous sites, and extra attention and caution should be exercised during the surgical planning phases of implant surgery.